It is known to use a mechanical clutch to disconnect a transfer device, of the type disclosed in U.S. Pat. No. 4,513,602 issued Apr. 30, 1985, from the prime mover therefor. As disclosed in said patent, the transfer mechanism is powered by the press itself and comprises reciprocating work gripping and handling jaws that transfer workpieces within the press.
When an electric servo drive is used as the power source for the transfer device, such servo drives have utilized only an electrical disconnect in the form of a current sensor in the servo motor energization circuit that senses an increase in armature current in the motor cicuit due to motor overload. However, modern high speed presses and transfer mechanisms require faster and more positive disconnect in the event of malfunction of the press or transfer mechanism to preclude "crashing" thereof.